A perpetual calendar of a timepiece, such as a watch, is designed to correctly display the date, taking into account the number of days in each month of the year and the occurrence of leap years, which include an extra day, i.e., February 29.
Certain electronic watches have perpetual calendars in which the parameters governing the display of the month, date and year are accessible only to the manufacturer of the watch or an experienced specialist, i.e., a watch repairman. These parameters are stored in the electronic circuit for later use. The operation of entering the parameters into the memory is called programming of the watch.
Various means exist for engaging the programming mode. The most common method is to use an external device that is available to only a select group, such as the watch manufacturer or its dealers and watch repairmen. An alternative approach is to build into the timepiece integrated elements that are necessary to carry out this programming.
If the ability to program a feature of the timepiece is built into the timepiece, it is desirable that an access code be provided, which is known by only a select group, so as to prevent erroneous programming by inexperienced or unknowledgeable persons. Applicant has developed a system described in Swiss patent application 4385/87-0, whereby a time-setting rod found on the timepiece is used to engage the programming mode and to make a parameter to be programmed correspond to each of three positions of this time-setting rod. The access code for a desired feature is entered by performing an unusual manipulation of this time-setting rod.
When a watch battery needs to be replaced, one of two situations can occur: 1) the watchmaker belongs to the aforementioned selected group and thus know how to access the programming mode as well as the programming of the watch itself, or 2) the watchmaker does not belong to the selected group and thus does not know how to access the programming mode of the watch.